1. Field of the Invention
The present invention relates to a method of fabricating a semiconductor device, by which a Cu line having a Cu/Hf interface with excellent characteristics can be formed by using Hf (hafnium), an efficient oxygen scavenger or gatherer, to remove oxygen (in the form of a Cu oxide layer) adhering to the Cu line.
2. Discussion of the Related Art
Generally, Cu is a popular material in connecting metal lines. Yet, a top layer (i.e., a wiring portion between a bonding pad and a package on packaging) employs Al as it is. Since a Cu surface is very oxidizable, oxygen can diffuse into a lower metal layer through the oxidized Cu surface to trigger corrosion of Cu included in the lower layer. Moreover, it is well know that an Al pad is very advantageous for wiring on packaging.
FIG. 1 is a cross-sectional diagram of conventional Cu wiring. Referring to FIG. 1, a Cu line 11 is embedded in a first insulating layer 12. A second insulating layer 13 of oxide, nitride, or polymer is formed on the first insulating layer 12. A barrier layer 14 and an Al layer 15 are stacked on the Cu line 11 in turn. In this case, RF etch pre-cleaning or chemical wet cleaning is performed on the Cu line 11 to remove a Cu oxide layer from a surface of the Cu line 11.
However, the conventional metal wiring process sometimes fails to remove the oxide on the Cu surface, or at other times over-etches the Cu line to cause degradation to the Cu line in the lower layer.